content: /*
  Copyright 2006 Jerry Huxtable
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
     http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  */
  
  package com.jhlabs.image;
  
  import java.awt.*;
  import java.awt.image.*;
  import com.jhlabs.composite.*;
  
  /**
   * Edge detection via the Laplacian operator.
   * @author Jerry Huxtable
   */
  public class LaplaceFilter extends AbstractBufferedImageOp {
  
      private void brightness( int[] row ) {
          for ( int i = 0; i < row.length; i++ ) {
              int rgb = row[i];
              int r = rgb >> 16 & 0xff;
              int g = rgb >> 8 & 0xff;
              int b = rgb & 0xff;
              row[i] = (r + g + b) / 3;
          }
      }
  
      public BufferedImage filter( BufferedImage src, BufferedImage dst ) {
          int width = src.getWidth();
          int height = src.getHeight();
  
          if ( dst == null )
              dst = createCompatibleDestImage( src, null );
  
          int[] row1 = null;
          int[] row2 = null;
          int[] row3 = null;
          int[] pixels = new int[width];
          row1 = getRGB( src, 0, 0, width, 1, row1 );
          row2 = getRGB( src, 0, 0, width, 1, row2 );
          brightness( row1 );
          brightness( row2 );
          for ( int y = 0; y < height; y++ ) {
              if ( y < height-1) {
                  row3 = getRGB( src, 0, y+1, width, 1, row3 );
                  brightness( row3 );
              }
              pixels[0] = pixels[width-1] = 0xff000000;//FIXME
              for ( int x = 1; x < width-1; x++ ) {
                  int l1 = row2[x-1];
                  int l2 = row1[x];
                  int l3 = row3[x];
                  int l4 = row2[x+1];
  
                  int l = row2[x];
                  int max = Math.max( Math.max( l1, l2 ), Math.max( l3, l4 ) );
                  int min = Math.min( Math.min( l1, l2 ), Math.min( l3, l4 ) );
  
                  int gradient = (int)(0.5f * Math.max( (max - l), (l - min) ));
  
                  int r = ((row1[x-1] + row1[x] + row1[x+1] +
                      row2[x-1] - (8 * row2[x]) + row2[x+1] +
                      row3[x-1] + row3[x] + row3[x+1]) > 0) ?
                          gradient : (128 + gradient);
                  pixels[x] = r;
              }
              setRGB( dst, 0, y, width, 1, pixels );
              int[] t = row1; row1 = row2; row2 = row3; row3 = t;
          }
  
          row1 = getRGB( dst, 0, 0, width, 1, row1 );
          row2 = getRGB( dst, 0, 0, width, 1, row2 );
          for ( int y = 0; y < height; y++ ) {
              if ( y < height-1) {
                  row3 = getRGB( dst, 0, y+1, width, 1, row3 );
              }
              pixels[0] = pixels[width-1] = 0xff000000;//FIXME
              for ( int x = 1; x < width-1; x++ ) {
                  int r = row2[x];
                  r = (((r <= 128) &&
                        ((row1[x - 1] > 128) ||
                         (row1[x] > 128)         ||
                         (row1[x + 1] > 128) ||
                         (row2[x - 1] > 128) ||
                         (row2[x + 1] > 128) ||
                         (row3[x - 1] > 128) ||
                         (row3[x] > 128)         ||
                         (row3[x + 1] > 128))) ?
                       ((r >= 128) ? (r - 128) : r) : 0);
  
                  pixels[x] = 0xff000000 | (r << 16) | (r << 8) | r;
              }
              setRGB( dst, 0, y, width, 1, pixels );
              int[] t = row1; row1 = row2; row2 = row3; row3 = t;
          }
  
          return dst;
      }
  
  	public String toString() {
  		return "Edges/Laplace...";
  	}
  }
  